The present specification relates to optical systems.
Chromatic dispersion (“CD”) is typically caused by different frequency components of optical signals having slightly different group velocities when transmitted through a chromatically dispersive medium. As a result, different frequency components of a transmitted optical signal can propagate at different speeds, thus arriving at a receiver at slightly different times. Chromatic dispersion can degrade performance in fiber optic systems by increasing the system bit error rate. Chromatic dispersion can be either negative or positive depending upon the transmission medium. For example, the group velocities of components of an optical signal in one medium can be higher for components having a higher frequency (positive chromatic dispersion) while in another medium the group velocities can be lower for components having a higher frequency (negative chromatic dispersion).
Fiber optical systems having different bit rates typically have different chromatic dispersion tolerance requirements. For a conventional system, the higher the bit rate the smaller the chromatic dispersion tolerance of the system. For example, in a conventional 10 Gbps system the CD tolerance can be about 500 ps/nm while in a conventional 40 Gbps system the CD tolerance can be about 30 ps/nm. To reduce the amount of chromatic dispersion in fiber optical systems, dispersion compensation modules (“DCMs”) can be used. A DCM typically provides a chromatic dispersion opposite in sign and equal in magnitude to the dispersion that a transmitted optical signal experiences. Conventional technologies for implementing DCMs include using dispersion compensation fiber and fiber Bragg gratings.